Merge pull request #117 from GenerationSoftware/gen-1768-28-drawtimeo…

…utat-is-one-draw-early-compared-to-what-the

Enforce minimum draw timeout and clarify natspec

src/PrizePool.sol

@@ -12,6 +12,13 @@ import { DrawAccumulatorLib, Observation, MAX_OBSERVATION_CARDINALITY } from "./
 import { TieredLiquidityDistributor, Tier } from "./abstract/TieredLiquidityDistributor.sol";
 import { TierCalculationLib } from "./libraries/TierCalculationLib.sol";
 
+/* ============ Constants ============ */
+
+// The minimum draw timeout. A timeout of two is necessary to allow for enough time to close and award a draw.
+uint24 constant MINIMUM_DRAW_TIMEOUT = 2;
+
+/* ============ Errors ============ */
+
 /// @notice Thrown when the prize pool is constructed with a first draw open timestamp that is in the past
 error FirstDrawOpensInPast();
 
@@ -89,8 +96,10 @@ error InvalidPrizeIndex(uint32 invalidPrizeIndex, uint32 prizeCount, uint8 tier)
 /// @notice Thrown when there are no awarded draws when a computation requires an awarded draw.
 error NoDrawsAwarded();
 
-/// @notice Thrown when the Prize Pool is constructed with a draw timeout of zero
-error DrawTimeoutIsZero();
+/// @notice Thrown when the prize pool is initialized with a draw timeout lower than the minimum.
+/// @param drawTimeout The draw timeout that was set
+/// @param minimumDrawTimeout The minimum draw timeout
+error DrawTimeoutLtMinimum(uint24 drawTimeout, uint24 minimumDrawTimeout);
 
 /// @notice Thrown when the Prize Pool is constructed with a draw timeout greater than the grand prize period draws
 error DrawTimeoutGTGrandPrizePeriodDraws();
@@ -280,7 +289,7 @@ contract PrizePool is TieredLiquidityDistributor {
   /// @notice The timestamp at which the first draw will open.
   uint48 public immutable firstDrawOpensAt;
 
-  /// @notice The maximum number of draws that can be missed before the prize pool is considered inactive.
+  /// @notice The maximum number of draws that can pass since the last awarded draw before the prize pool is considered inactive.
   uint24 public immutable drawTimeout;
 
   /// @notice The address that is allowed to set the draw manager
@@ -335,8 +344,8 @@ contract PrizePool is TieredLiquidityDistributor {
       params.grandPrizePeriodDraws
     )
   {
-    if (params.drawTimeout == 0) {
-      revert DrawTimeoutIsZero();
+    if (params.drawTimeout < MINIMUM_DRAW_TIMEOUT) {
+      revert DrawTimeoutLtMinimum(params.drawTimeout, MINIMUM_DRAW_TIMEOUT);
     }
 
     if (params.drawTimeout > params.grandPrizePeriodDraws) {

test/PrizePool.t.sol

@@ -20,7 +20,8 @@ import {
   PrizeIsZero,
   ConstructorParams,
   InsufficientRewardsError,
-  DrawTimeoutIsZero,
+  DrawTimeoutLtMinimum,
+  MINIMUM_DRAW_TIMEOUT,
   DrawTimeoutGTGrandPrizePeriodDraws,
   PrizePoolNotShutdown,
   DidNotWin,
@@ -160,9 +161,18 @@ contract PrizePoolTest is Test {
     assertEq(prizePool.drawPeriodSeconds(), drawPeriodSeconds);
   }
 
-  function testDrawTimeoutIsZero() public {
+  function testDrawTimeoutLtMinimum() public {
     params.drawTimeout = 0;
-    vm.expectRevert(abi.encodeWithSelector(DrawTimeoutIsZero.selector));
+    vm.expectRevert(abi.encodeWithSelector(DrawTimeoutLtMinimum.selector, 0, 2));
+    new PrizePool(params);
+
+    params.drawTimeout = 1;
+    vm.expectRevert(abi.encodeWithSelector(DrawTimeoutLtMinimum.selector, 1, 2));
+    new PrizePool(params);
+
+    assertEq(MINIMUM_DRAW_TIMEOUT, 2); // validate assumptions
+    params.drawTimeout = 2;
+    // no revert
     new PrizePool(params);
   }